Examples of articles which easily deteriorate or degrade under the effect of oxygen include foods, beverages, medicinal products and cosmetics. For the purpose of preventing oxidation of such articles with oxygen, thereby storing them for a long term, oxygen absorbents, which remove oxygen within packaging bodies storing these articles, are used.
As the oxygen absorbent, an oxygen absorbent containing an iron powder as a reactive base compound (hereinafter, referred to also as “iron-based oxygen absorbent”) is generally used in view of oxygen-absorbing ability, handling and safety. However, the iron-based oxygen absorbent is responsive to a metal detector and thus it is difficult to inspect packaging bodies containing the iron-based oxygen absorbent for a foreign matter by using a metal detector. Furthermore, packaging bodies containing an iron-based oxygen absorbent have a risk of ignition, and thus, they cannot be heated by a microwave oven. Moreover, the oxidation reaction of an iron powder requires water, and thus, an oxygen-absorbing effect is exerted only when a preserve is rich in moisture content.
Packaging containers are developed by making the container of a multilayered material having an oxygen-absorbing layer formed of an oxygen-absorbing resin composition containing a thermoplastic resin and an iron-based oxygen absorbent, thereby improving a gas barrier property of the container and providing an oxygen-absorbing function to the container itself (see, for example, Patent Document 1). However, this container have the same problems: since an iron-based oxygen absorbent is responsive to a metal detector, a foreign matter cannot be inspected by using a metal detector; a microwave oven cannot be used for heating and an effect is only exerted in a preserve having a high moisture content. In addition, the container is opaque. Due to this, the container has a problem in that visibility of content is insufficient.
In the aforementioned circumstances, it has been desired to develop an oxygen absorbent containing an organic substance as a reactive base compound. As the oxygen absorbent containing an organic substance as a reactive base compound, an oxygen absorbent containing ascorbic acid as a base compound is known (see, for example, Patent Document 2).
In the meantime, an oxygen-absorbing resin composition, which is composed of a resin and a transition metal catalyst, having an oxygen trapping property is known. For example, a resin composition composed of a polyamide, in particular, a xylylene group-containing polyamide, serving as an oxidizing organic component, and a transition metal catalyst, is known (see, for example, Patent Document 3). In Patent Document 3, articles obtained by molding such a resin composition, such as an oxygen absorbent, a packaging material and a multilayer laminated film for packaging are further exemplified.
As an oxygen-absorbing resin composition requiring no moisture content for absorbing oxygen, an oxygen-absorbing resin composition composed of a resin having a carbon-carbon unsaturated bond and a transition metal catalyst, is known (see, for example, Patent Document 4).
As a composition for trapping oxygen, a composition composed of a polymer containing a substituted cyclohexene ring or a low molecular-weight substance bound with the cyclohexene ring and a transition metal is known (see, for example, Patent Document 5).